Two experiments were carried out on rats to determine the nutritional value of raw and autoclaved amaranth (Amaranthus retroflexus) seeds. The test groups of the first experiment were fed only ground amaranth seed. The control group received pure maize meal. Both test groups showed higher growth rate than the control group, due to the higher protein content of amaranth. The final body weight of rats fed autoclaved amaranth seed significantly exceeded that of rats fed raw amaranth seed. The Net Protein Utilisation (NPU) index of raw and autoclaved amaranth was determined in the second experiment. The diets had 10% crude protein concentration and the only protein source was the meal of raw and autoclaved amaranth seed. It was found that the heat treatment of amaranth increased the body weight gain of rats even when the animals consumed diets containing only 10% crude protein. The feed consumption was also higher with the diet containing autoclaved seeds. Despite the finding that there was no significant difference in the NPU index, data suggest the presence of a heat-labile antinutritive compound.